The present invention relates to an interface circuit that connects a computer and peripheral units, more particularly, to the power control means for said interface circuit.
Generally, an interface circuit is used for connecting a computer, for example, a personal computer, and peripheral equipment, for example, a CRT display. Such an interface circuit has a plurality of signal paths for connecting two units for either transmitting or receiving signals and has signal path control circuits. In such a case, the interface circuit may be built into the computer unit.
Conventionally, if a computer, for example, a portable computer, is driven by a battery which concurrently drives an interface circuit, the battery capacity should be expanded, thus requiring a battery unit of greater dimension. Since existing interface units usually contain both the signal converter and oscillator circuits that consume much power during operation, the computer and interface units are usually independently driven by their own battery.
Such a system, however, still has a problem to solve. When the computer and interface units are independently driven, each having their own battery since the operator may occassionally forget to turn the power off from the interface, the battery power may be dissipated without effect in the interface unit.